Hi Flashcards
What is a chemical change?
Formation of a new substance
What is effervescence
When a chemical reaction fizzes
What is carbon dioxide gas?
Lumps of chalk are reacting with hydrochloric acid
What is precipitation?
Some reactions between solutions produce a solid
What is precipitate?
The solid formed in precipitation reaction.
What is exothermic reaction?
Reactions that give out heat
What is combustion?
The process of burning sth
What is an endothermic reaction?
Any chemical reaction that absorbs heat from its environment
What is an reactant in a chemical reaction?
The substance we start with in a chemical reaction are called reactants
What is the product?
The new substance formed in a chemical reaction
Why are word equations useful in a chemical reaction?
Word equations are a useful way of describing chemical reactions.
What is a physical change?
Physical changes are different from chemical changes in that no new substance are formed during the change
What are mixing substances?
Mixing substances can be described as a physical change. If no new substances are produced it is usually quite easy to separate the substances in a mixture.
What are the mixtures in air?
A mixture of gases including oxygen, nitrogen, argon and carbon dioxide
What are the mixtures in sea water?
A mixture of water , salt and other dissolved substances
What are the mixtures in soil?
A mixture of rock fragments ,water,dissolved minerals, air and humus
What are the mixtures in rocks
A mixture of different minerals
What are the changes of state?
Melting,boiling,evaporation,condensation and freezing.
What is matter?
Matter is the scientific word used to describe all the different types of substances and materials found in our universe.
What is the particles theory?
All matter is composed of tiny indivisible particles too small to see
What is a atom?
The simplest particle
What is the diameter of the largest atom?
0.00 000 000 5.
What are molecules?
Two or more atoms joined together
How do you change a state
Heating/cooling
What happens to the particles when a substance is heated?
When a substance is heated the particles have more energy and move faster so the temperature rises.
What happens to the particles when a substance is cooled?
When a substance is cooled the particles have less energy and move slower so the temperature falls
What is melting?
When the particles vibrate fast enough to break free from each other
What is evaporation?
When the particles at the surface of the liquid vibrate fast enough to escape and form
What is boiling?
The process by which a liquid turns into a Vapor when it is heated to its boiling point.
What is condensation?
The process by which water Vapor in the air is changed into liquid water.
What is freezing?
When a liquid is cooled,heat energy is removed from the particles making them move more slowly.If the cooling is continued long enough the particles will eventually not be able to move about this is called freezing and a solid is formed
What is sublimation?
(Gas to Solid) the conversion between the solid and the gaseous phases of matter, with no intermediate liquid stage.
What is diffusion?
Diffusion occurs when the particles of one substance spread out and mix with the particles of another substance
What is expansion?
When a substance gets bigger and takes up more space
What is contraction?
When a substance gets smaller and takes up less space
What is density?
Mass per unit volume
What is air pressure
The force exerted on a surface by the air above it is gravity pulls it to earth
How can we measure air pressure?
By using a barometer
What is the unit of measuring air pressure?
Pascals
What does a vacuum pump do?
A vacuum pump can be used to remove the air from inside a container
