Heat Flashcards
why does a metal ball not fit/fit through a ring after it is heated/cooled.
The metal ball is matter. Thus, when the ball gains/lose heat, it will expand/contract.
identical pieces of butter were put on blocks P and Q, made of different materials. After the blocks were heated with a hot plate, it took the butter of P 13 seconds while the butter on Q took 50 seconds.
Which material is a better conductor of heat and explain why.
P. The time for the butter to melt completely is shorter than Q, so P gains heat from the hot plate and transfers it to the butter faster than Q.
sally puts her (ice cream cake) in a box with 3 gel packs. Explain how the gel packs helps to lower the temperature of the air in the box and keep the (ice cream cake) frozen/cold for a longer time
The cold gel pack will gain heat from the surrounding air in the box and keep the surrounding air cool for the longest time possible to keep the (ice cream cake) cooler for a longer time.
Explain why the temperature of the water in the double-walled glass decreased more slowly than that in the single-walled glass.
The air between the double-walled glass is a poor conductor of heat. Thus, the air slows down the transfer of heat from the water to the surroundings.
how is evaporation different from boiling?
- Evaporation takes place at any temperature but boiling takes place at a fixed temperature.
- Boiling takes place throughout the liquid while evaporation takes place at the surface of the liquid.
A glass tube with a drop of ink connects two beaker A and B.
What can be done to move the ink drop closer to B? Why?
You could place beaker A in a tub of hot water. The air inside beaker A would gain heat and expand, pushing the ink drop closer to B.
A thermometer is placed inside a wool glove. Would the thermometer show a higher, lower or same temperature as a thermometer as a thermometer outside the glove? Why? It would have the same temperature.
The glove is not a heat source. The inside of the glove is the same temperature as the outside of the glove.
A snow man under the sun is wrapped in a jacket. Being under the sun, would a snow man wrapped in a jacket melt at a faster, slower or at the same rate as a snowman without a jacket? Why?
It would melt at a slower rate. The snowman wrapped in a jacket would gain heat from the surroundings slower as the jacket is a poor conductor of heat.
The temperature of the air inside an occupied room with windows on both sides open is colder then then when only the windows on one side are. Explain why.
The people in the room lose heat to the surrounding air in the room. With the windows on one side of the room, closed hot air escapes slower from the room. Hence, less cold air enters the room to displace the hot air.
When railway tracks are laid, small gaps are left between the metal rails. Explain why this is important, especially on a hot day.
The metal rails are matter. The gap allows space for the metal rails to expand when it gains heat from the surroundings on a hot day. This prevents the rails from buckling.
In countries with four season, the power lines are observed to be hung loosely during hot weather. Explain why this is important.
During cold weather, the power line loses heat to the surrounding air and contracts. Hanging it loosely prevents it from snapping.
Water was boiled in a pot over a flame. At the 4th minute, the water remained constant at a 100 degrees until the 10th minute where it started decreased until the 15 min to 30 degrees.
It was claimed that the water did not gain heat from the fourth to 10th minute as the temperature of the water stayed constant. Do you agree. Explain why.
At which minute did the flame switched off. Give a reason for your answer
No. Heat was gained by the water to boil and turned into steam.
10th minute. The temperature of the water starts to drop as the water loses heat to the surroundings
(a) A bimetallic strip made of Metal A on top and B below is heated over a fire. After heating, the bimetallic strip bent upwards.
Explain why.
(b) A fire alarm circuit has to contact points that are separated from each other at room temperature. One is connected to the bimetallic strip above that is held in place by a holder. Explain how the fire alarm will ring to alert people during a fire.
(a) Metal A and B gained heat from the fire and expand at different rates. Metal A bends at a faster rate than Metal B, causing the bimetallic strip to bend upwards after heating.
(b) The bimetallic strip will gain heat and expand, causing the bimetallic strip to bend towards the contact points. A closed circuit is formed and electricity an flow through the alarm, causing the alarm to ring.
A glass bottle filled with colored water had a glass tubing attached to the top.it was observed that the water level in the tube decreases initially and then rise again after the bottle was placed in hot water. Explain why it happened.
The glass bottle gains heat from the hot water and expands. This causes the water level to decreases. After some time, the colored water in the glass bottle gains heat and expands causing the water level to rise.
3 students made some statements about a bigger ice cube A and a smaller ice cube B in the fridge. Michael said since A is bigger it should be colder than ice cube B. Siti said while both A and B are at the same temperature, A has more heat energy. Xin Hai said both A and B have the same amount of heat energy since both of them are in the fridge.
Which pupil do you think is correct. Explain your answer.
Siti is correct. Since both ice cubes are in the fridge, they have the same temperature. However, with Ice cube A having a greater mass, it will have more heat energy as compared to ice cube B.
Three identical set ups were made. A flask with a stopper and a narrow glass tube inserted through the stopper was filled with liquid X so that the height of liquid X in the stopper was at a certain height. Set up A was immersed in water of 50 degrees, B 7-0 degrees, C 90 degrees for 5 min.
(a)Arrange the set ups by height of liquid X from highest to shortest after 5 min.
(b)It was noticed that the height of the liquid in the glass tube in set up C dropped for the first 2 seconds when the flask was placed in the water. Explain why.
(c)Set up D was identical to Set up A but only half the volume of water was used. Give reason why it took a longer time for liquid X in Set up D to reach the same height as in set up A
(a) A, B, C
(b)The glass flask gained heat from the water and expanded first before liquid X.
(c) With a smaller a volume of water in wet up D, there is less heat energy in the water than in Set up A. Hence, Liquid X takes a longer time to gain heat and expand to to the same height as in set up A.
