Gravity is a force which tries to pull two objects toward each other. Anything which has mass also has a gravitational pull. The more massive an object is, the stronger its gravitational pull is. Earth's gravity is what keeps you on the ground and what causes objects to fall.
1st and 4th options are suitable answers, as these 2 changes are not exactly physical changes as it cant return back to original form and as well as its not cooling, so I feel its 1st and 4th options
The melting point of potassium = 
Melting point of titanium = 
Titanium has a stronger metallic bonding compared to potassium. Titanium being a transition metal has greater number of valence electrons (4 valence electrons) contributing to the valence electron sea compared to potassium which has only one valence electron. The atomic size of Titanium much lower than that of potassium, so the bonding between Titanium atoms is stronger than that of potassium. Hence, the melting point of Titanium is much higher than that of potassium.
Answer:
B
Explanation:
cool air never rises so not A
C would mean its getting warmer
and heat flows from warm to cool so not D
we are left with B
if my anwser helps please mark as brainliest.
A reaction is exothermic if Δ<em>H</em> (or
in some textbooks) is negative:
- H₂ + Br → 2 HBr, ΔH < 0.
- CH₄ + 2 O₂ → CO₂ + 2 H₂O, ΔH < 0.
A reaction is endothermic if Δ<em>H</em> is positive:
- 2 NH₃ → N₂ + 3 H₂, ΔH > 0.
- 2 HCl → H₂ + Cl₂ ΔH > 0.
<h3>Explanation</h3>
The enthalpy of a system is the sum of its internal energy. ΔH < 0 indicates that the reactants lose internal energy in the reaction. Energy conserves, and those internal energies must have converted to some other form of energy. They typically end up as thermal energy. The reaction will release heat since it is exothermic.
Similarly, ΔH > 0 indicates that the reactants gains internal energy in the reaction. Energy conserves. As a result, the reaction must have gained energy from its surroundings. The reaction will be endothermic since it absorbs heat.