Physical properties
Define density.
Density is the mass per unit volume.
Name the measuring instrument to measure short distances with an accuracy of 2 decimal place.
vernier caliper
Give an example of physical change.
boiling water
tearing paper
water cycle
Acids turn litmus paper _______.
red
Balance the equation
___ C + ___ O2 = ___ CO2
___ C + ___ O2 = ___ CO2
A substance can scratch glass easily. This property is classified as _____ of a material.
hardness
Which part of the Vernier caliper do you use to measure external diameter?
external jaws
What is one difference between physical and chemical change?
physical change - no new substance is formed ; no heat or light is given off or taken in ; change is reversible
Acids reacts with alkali to form water and salt. This process is called _________.
neutralisation
Give 2 properties of acids.
sour taste
turns blue litmus red
reacts with alkali to form salt and water
reacts with metal to form salt and hydrogen
reacts with carbonate to form salt, water and carbon dioxide
Give 2 reasons why you use metals to make cooking utensils.
high melting point
good thermal conductor
Name the instruments you need to find density of ice.
electronic balance and measuring cylinder
Describe how do you test for carbon dioxide gas.
Pass the gas into limewater. A white precipitate is formed.
Name the products formed when calcium carbonate reacts with hydrochloric acid.
calcium carbonate, carbon dioxide and water
blue
The density of 3 liquids are
A: 1.09 g/cm3, B: 4.01 g/cm3 and C:0.89 g/cm3. Reorder the liquids in ascending order.
CAB
To measure the volume of a small marble in the science laboratory, we can use a ______.
measuring cylinder
Describe how do you test for hydrogen gas.
Place a lighted splint at the mouth of the test tube. The flame extinguished with a pop sound.
Balance the chemical equation
___ Ca +___ O2 = ___ CaO
_2__ Ca +___ O2 = _2__ CaO
red
The mass of substance X is 800 g. It has a volume of 1 000 cm3. Will substance X sink or float in liquid Y which has a density of 0.89 g/cm3?
float
Sodium reacts with hydrochloric acid to form _____ and hydrogen.
sodium chloride
The products of electrolysis of water are ____ and ___.
hydrogen and oxygen
Balance the chemical reaction
___ H2 +___ O2 = ___ H2O
_2__ H2 +___ O2 = _2__ H2O
Why do you use toothpaste to brush your teeth?
Food left behind is acidic in nature. Toothpaste is alkali and will neutralise the acid formed, thus preventing tooth decay.